On Mon, Feb 27, 2012 at 12:38:47PM -0800, Dan Williams wrote: > An experimental hack to tease out whether we are continuing to > run the softirq handler past the point of needing scheduling. > > It allows only one trip through __do_softirq() as long as need_resched() > is set which hopefully creates the back pressure needed to get ksoftirqd > scheduled. > > Targeted to address reports like the following that are produced > with i/o tests to a sas domain with a large number of disks (48+), and > lots of debugging enabled (slub_deubg, lockdep) that makes the > block+scsi softirq path more cpu-expensive than normal. > > With this patch applied the softlockup detector seems appeased, but it > seems odd to need changes to kernel/softirq.c so maybe I have overlooked > something that needs changing at the block/scsi level? But stucking in softirq for 22s still seems odd. I guess the reason why your patch works is that softirq returns before handling BLOCK_SOFTIRQ, but who knows, just guess. Does kernel command line 'threadirqs' solve your issue? Thanks, Yong > > BUG: soft lockup - CPU#3 stuck for 22s! [kworker/3:1:78] > Modules linked in: nls_utf8 ipv6 uinput sg iTCO_wdt iTCO_vendor_support ioatdma dca i2c_i801 i2c_core wmi sd_mod ahci libahci isci libsas libata scsi_transport_sas [last unloaded: scsi_wait_scan] > irq event stamp: 26260303 > hardirqs last enabled at (26260302): [<ffffffff814becf4>] restore_args+0x0/0x30 > hardirqs last disabled at (26260303): [<ffffffff814c60ee>] apic_timer_interrupt+0x6e/0x80 > softirqs last enabled at (26220386): [<ffffffff81033edd>] __do_softirq+0x1ae/0x1bd > softirqs last disabled at (26220665): [<ffffffff814c696c>] call_softirq+0x1c/0x26 > CPU 3 > Modules linked in: nls_utf8 ipv6 uinput sg iTCO_wdt iTCO_vendor_support ioatdma dca i2c_i801 i2c_core wmi sd_mod ahci libahci isci libsas libata scsi_transport_sas [last unloaded: scsi_wait_scan] > > Pid: 78, comm: kworker/3:1 Not tainted 3.3.0-rc3-7ada1dd-isci-3.0.183+ #1 Intel Corporation ROSECITY/ROSECITY > RIP: 0010:[<ffffffff814be8b6>] [<ffffffff814be8b6>] _raw_spin_unlock_irq+0x34/0x4b > RSP: 0000:ffff8800bb8c3c50 EFLAGS: 00000202 > RAX: ffff8800375f3ec0 RBX: ffffffff814becf4 RCX: ffff8800bb8c3c00 > RDX: 0000000000000001 RSI: ffff880035bbc348 RDI: ffff8800375f4588 > RBP: ffff8800bb8c3c60 R08: 0000000000000000 R09: ffff880035aed150 > R10: 0000000000018f3b R11: ffff8800bb8c39e0 R12: ffff8800bb8c3bc8 > R13: ffffffff814c60f3 R14: ffff8800bb8c3c60 R15: 0000000000000000 > FS: 0000000000000000(0000) GS:ffff8800bb8c0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: 0000000000f2e028 CR3: 00000000b11b3000 CR4: 00000000000406e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process kworker/3:1 (pid: 78, threadinfo ffff8800377d2000, task ffff8800375f3ec0) > Stack: > ffff88003555f800 ffff88003555f800 ffff8800bb8c3cc0 ffffffffa00512c4 > ffffffff814be8b2 ffff880035dfc000 ffff880035dfe000 000000000553a265 > ffff8800bb8c3cb0 ffff88003555f800 ffff8800b20af200 ffff880035dfe000 > Call Trace: > <IRQ> > [<ffffffffa00512c4>] sas_queuecommand+0xa7/0x204 [libsas] > [<ffffffff814be8b2>] ? _raw_spin_unlock_irq+0x30/0x4b > [<ffffffff8132b6a9>] scsi_dispatch_cmd+0x1a2/0x24c > [<ffffffff813317a8>] ? spin_lock+0x9/0xb > [<ffffffff813333b0>] scsi_request_fn+0x3b1/0x3d9 > [<ffffffff8124a19f>] __blk_run_queue+0x1d/0x1f > [<ffffffff8124b869>] blk_run_queue+0x26/0x3a > [<ffffffff813319a5>] scsi_run_queue+0x1fb/0x20a > [<ffffffff81332136>] scsi_next_command+0x3b/0x4c > [<ffffffff81332b66>] scsi_io_completion+0x205/0x44f > [<ffffffff813316b8>] ? spin_unlock_irqrestore+0x9/0xb > [<ffffffff8132b3ab>] scsi_finish_command+0xeb/0xf4 > [<ffffffff81333a04>] scsi_softirq_done+0x112/0x11b > [<ffffffff812540ac>] blk_done_softirq+0x7e/0x96 > [<ffffffff81033e0c>] __do_softirq+0xdd/0x1bd > [<ffffffff814c696c>] call_softirq+0x1c/0x26 > [<ffffffff81003ce6>] do_softirq+0x4b/0xa5 > [<ffffffff81034916>] irq_exit+0x55/0xc2 > [<ffffffff814c6a9c>] smp_apic_timer_interrupt+0x7c/0x8a > [<ffffffff814c60f3>] apic_timer_interrupt+0x73/0x80 > <EOI> > [<ffffffff814be8b6>] ? _raw_spin_unlock_irq+0x34/0x4b > [<ffffffffa00512c4>] sas_queuecommand+0xa7/0x204 [libsas] > [<ffffffff814be8b2>] ? _raw_spin_unlock_irq+0x30/0x4b > [<ffffffff8132b6a9>] scsi_dispatch_cmd+0x1a2/0x24c > [<ffffffff813317a8>] ? spin_lock+0x9/0xb > [<ffffffff813333b0>] scsi_request_fn+0x3b1/0x3d9 > [<ffffffff8124a19f>] __blk_run_queue+0x1d/0x1f > [<ffffffff8125f3bb>] cfq_kick_queue+0x2f/0x41 > [<ffffffff8104462e>] process_one_work+0x1c8/0x336 > [<ffffffff81044599>] ? process_one_work+0x133/0x336 > [<ffffffff81044306>] ? spin_lock_irq+0x9/0xb > [<ffffffff8125f38c>] ? cfq_init_queue+0x2a3/0x2a3 > [<ffffffff81045fd9>] ? workqueue_congested+0x1e/0x1e > [<ffffffff81046085>] worker_thread+0xac/0x151 > [<ffffffff81045fd9>] ? workqueue_congested+0x1e/0x1e > [<ffffffff8104a618>] kthread+0x8a/0x92 > [<ffffffff8107654e>] ? trace_hardirqs_on_caller+0x16/0x16d > [<ffffffff814c6874>] kernel_thread_helper+0x4/0x10 > [<ffffffff814becf4>] ? retint_restore_args+0x13/0x13 > [<ffffffff8104a58e>] ? kthread_create_on_node+0x14d/0x14d > [<ffffffff814c6870>] ? gs_change+0x13/0x13 > > Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Cc: Jens Axboe <axboe@xxxxxxxxx> > Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx> > Reported-by: Lukasz Dorau <lukasz.dorau@xxxxxxxxx> > Reported-by: Andrzej Jakowski <andrzej.jakowski@xxxxxxxxx> > Not-yet-signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > --- > kernel/softirq.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/kernel/softirq.c b/kernel/softirq.c > index 4eb3a0f..82a3f43 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -255,7 +255,7 @@ restart: > local_irq_disable(); > > pending = local_softirq_pending(); > - if (pending && --max_restart) > + if (pending && --max_restart && !need_resched()) > goto restart; > > if (pending) > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Only stand for myself -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
